Polishing Characteristics of Mineral Aggregates : Technical Paper

Abstract

The majority of the highways which have been constructed recently, whether of portland cement or of bituminous materials Initially have exhibited good resistance to skidding for the critical design condition, which occurs when tha surface is wet* Unfortunately, for many of these pavements this initial skid resistance has been short-lived The anti-ekid properties of a well-designed pavement surface are dependent to a large degree u;x>n the polishing characteristics of the mineral ag« gregate or aggregates of which the paving mixture is composed,, Although the type of cene.iting agent, the gradation, and the openness of the sur« face have some effect upon the rate at which polishing progresses, the ultimate state of slipperiness is determined by the nature of wear of the pavement vAdch, in turn, is directly related to the resistance to polishing of the surface aggregate,. If highways are to be build which possess adequate anti-siid characteristics for a reasonable period of wear under the ever-increasing polishing effect of traffic, consideration must be given to the slipperiness potential of highway materials of which paving mixtures are composed, so that adequate skid resistance ray be included as a design parameter A laboratory investigation vas undertaken at Purdue University in an en-> deavor to contribute to a better understanding of some of the variables involved in pavement slipperinesso This paper is a report of a phase of

11. Aggregates in bituminous bound construction materials

“…In a study of the carbonate rocks Shupe & Lounsbury (1959) and Gray & Renninger (1963, 1965 demonstrated that a degree of impurity, as measured by the insoluble residue, significantly improves the polishing resistance. While this improvement correlated well with an increase in insoluble residue (consisting chiefly of quartz sand grains, mica and clay mineral matter) Gray and Renninger found that an even better correlation existed if the insolubles measured were restricted to those of sand size, i.e.…”

A Laboratory Investigation of the Phenomenon of Friction as Applied to Fine-Textured Bituminous Paving Mixtures

“…The possibility of using sharp, angular or crushed aggregate for increasing the skid resistance of pavement surfaces has been considered many times. Little actual test data are available to substantiate such possibilities, but limited tests by Shupe (78,79) indicate that after several polishing cycles, round aggregate may supply more skid resistance than angular. His explanation for this apparently little understood result was that the round aggregate compacted more readily and hence gave greater densities and thus had more aggregate in contact with the test shoe.…”